1. Field of the Invention
The invention relates to a receiver system for vehicles having a circuit for suppressing the receipt of an interference radiation emitted by these vehicles.
2. Description of the Prior Art
The interference radiation emitted by the vehicle body often leads to a considerable lowering of the quality of the receipt in the on board receiver system. Particularly in the range of the receipt of the middle and short wave (AM range) radio waves, the radio receipt is often strongly affected by audible pulse-like interferences.
Often the ignition system and digital components create a series of high intensity high frequency component radio waves that are received via an antenna and sent into a receiver. These radio waves are of such intensity that the antenna cannot be attached in the vicinity of the engine, or respectively any means causing strong interference radiation is not possible. In the praxis of automobile construction, by arranging the conduits or the input of means avoiding interference, it has been shown that the suppression of an interference emitting radiation through these measures is often not feasible or only feasible with high cost.
Thus, antenna systems for vehicles with front wheel engines are now disposed in the rear region. This is done to attain an improved interference distance with the aid of the larger distance from the main interference source. However, vehicle interferences are often so intensive that even in the case of antennas that are arranged away from the interference source, there is still noticeable interference.
In German Patent 24 60 227.5 there is shown a proposed solution to present vehicle interference with respect to the amount of phase in the HF range with the aid of control system and in superposition to the receiver signal of the receiver system. This receiver system is affected by the interference in that manner that the interference components in the receiver signal are cancelled. This method is very cost intensive and relies on the precise evaluation of the interference effective in the receiver antenna which is in many cases impossible.
Therefore, one object of the invention is to provide an effective and cost efficient arrangement so as to reduce the interference to render inaudible the receiver interferences which are associated with the interference radiation emitted by the entire vehicle, particularly in the frequency bands of amplitude modulated radio.
This aim is solved in accordance with the invention in a receiver system for vehicles. With the present invention, there is an advantage in that the determination of the time intervals, within which a series of received usable signals must be sampled. In this way, the interference from an interference radiation is not passed through the terminus device and is not determined in the received usable signals. The essence of the invention resides in that with the aid of one or more coupling elements, the interference radiation is taken up separately, and the signal corresponding to the received usable signals is rather small.
Thus from this invention it is possible to configure the shortest possible sampling time through the sampling of the received usable signals so that the interference is as small as possible. In the praxis it shows that there is often appreciable interference so that even with a strong received usable signal and a weak interference signal, interference free reception is rare. This applies particularly in periods when there is electrical ignition or when there are pulses of digital signals and especially in the AM radio range. Accordingly the invention is aimed to determine the time intervals of the appearance of pulse-like interferences, separated from the received usable signals, and to determine the sampling time points and the duration of sampling in accordance with the invention.
This is done with the aid of an interference signal receiving device. In addition there is also a coupling element for the uptake of the pulse-like interfering interference radiation emitted by the entire vehicle. Thus, the coupling element is positioned in the vehicle in such a manner and configured in such a way that its output signal predominantly contains the pulses leading to receiving interference of the interference radiation, wherein a component of the received usable signals is low so that the ratio of the component of the receiving usable signals over the interference beam is at least 10 dB lower than the output of the antenna over the interference beam.